Compound miter saws of the motor driven type are well known cutting devices for performing both miter and bevel cuts. However, one disadvantage with such devices is that their maximum cutting length is limited by the diameter of the saw blade. This limitation requires the operator of the saw to re-position the work piece in order to complete a cut longer than the diameter of the saw blade.
To overcome this disadvantage, compound miter saws have been provided with slide mechanisms so that the saw blade can be moved laterally of the work piece to enable longer cuts to be made without the need to re-position the same. One such compound miter saw is described in U.S. Pat. No. 4,869,142 ('142 Patent).
In particular, the '142 Patent discloses a compound miter saw which includes a gear casing 13 rotatably mounted to a bracket 9 which is in turn, fixably attached to one end of a pair of laterally spaced, parallel slide bars 11. The slide bars are movably supported by a holder 7 so that saw blade can be selectively moved between its retracted and fully extended positions. The holder is carried by a turntable and is also pivotable vertically so that the saw blade may be positioned to any desired bevel angle at any miter cut angle.
The compound miter saw disclosed in the '142 Patent, however, has a number of drawbacks. In particular, when the saw blade is fully extended, the weight of the power saw combined with the downward movement of the saw, produces a downward momentum of the saw which results in vertical flexing and/or motion of the cantilever mounted bars. Additionally, the slide rods in the '142 Patent are supported within the holder 7 by a slide clearance fit. As such, when the saw is in the retracted position, the bottom surface of the slide rods are in contact with the housing while a clearance spacing exists between the top surface of the slide rods and the housing. When the saw blade is fully extended, the slide rods will rotate downward an amount proportional to the clearance spacing between the slide rods and the upper surface of the support housing in addition to flexing. In addition, as the forwardly rotating saw blade cuts the work piece there is an upward torque or "kick" which is also transmitted to the base 11. As a result of the above design features, the saw blade will tend to vibrate or oscillate vertically. When the saw blade is tilted to a substantial bevel angle, the effect of such vibration of the saw blade may prove even more troublesome because the vertical vibratory or oscillatory motion is at an oblique angle to the plane of the bevel cut. This will likely result in inconsistent cutting performance and unequal drag on opposite sides of the blade which may cause excessive heat to be generated and therefore greater blade wear. In addition, the friction contact between the slide rods and the housing may cause some difficulty for the operator in moving the saw blade smoothly and comfortably especially when cutting very dense and hard materials.
The principle object of this invention is to provide an improved compound miter saw of slidable construction which is capable of more consistent cutting performance even when the saw blade is fully extended and tilted for maximum bevel cuts.
Another object of the present invention is to provide an improved compound miter saw of slidable construction which has a slide mechanism that provides easier, smoother and more consistent cutting performance under all conditions than saws heretofore available.